2 cups (8-1/2 oz) unbleached all-purpose flour
1/2 cup (3-1/2 oz) granulated sugar
1 Tbsp baking powder
1 tsp salt
Grated zest of 1 lemon
1/2 cup (2 oz) chopped walnuts
1/2 cup (3 oz) raisins or currants
2 large eggs, beaten
1/2 cup (4 oz) milk
1/2 cup (3-1/2 oz) vegetable oil
1 cup (8-1/4 oz) packed shredded unpeeled zucchini
1/2 cup lemon curd
Additional walnuts, very finely chopped, for topping (optional)
Preheat oven to 400°F. Combine the flour, sugar, baking powder, salt, and lemon zest in a large bowl. Stir in the walnuts and raisins. In a smaller bowl (or a 2-cup liquid measure), combine the eggs, milk, and oil. Make a well in the center of the dry ingredients and add the wet ingredients. Stir just until barely combined, and then gently fold in the zucchini.
Spoon the batter into a greased 12-cup muffin tin and bake for 20-25 minutes, or until the muffins spring back when you press them with your fingertips. Remove from the oven, let cool for 5 minutes on a rack, then turn out of the pans to finish cooling.
When the muffins are cool, cut a small hole in the top of each one with a tiny melon baller or a knife, and fill the holes to overflowing with lemon curd. Top with a sprinkling of finely chopped walnuts.